#!/usr/bin/env bash
# SC2 regression decision — extracted from 99-dryrun.sh so the regression-FAIL detector is independently
# unit-testable (5d112cb). Given two SORTED failing-test-NAME files — the standalone extract's set and the
# in-repo baseline set — it prints the regressions (standalone failures absent from the baseline) and EXITS
# NON-ZERO (1) if any exist. The contract: "standalone failing set ⊆ in-repo failing set" (the extraction
# introduced NO new failure; pre-existing in-repo red is the plugin's own concern, not a migration regr).
# A missing capture file is a hard ERROR (exit 2), never a silent zero-regression PASS (guards 4044c49).
#
# Usage: sc2-regression.sh <standalone_fails_file> <baseline_fails_file>
set -u
sf="${1:?standalone fails file}"
bf="${2:?baseline fails file}"
[ -f "$sf" ] && [ -f "$bf" ] || { echo "SC2-REGRESSION ERROR: missing capture file ($sf / $bf)" >&2; exit 2; }

regr="$(comm -23 "$sf" "$bf")"
if [ -n "$regr" ]; then
  printf '%s\n' "$regr"
  exit 1
fi
exit 0